The invention relates to the making and processing of stationery and like products of the type wherein sheets of paper and/or other material are held together by a binder for pivotal movement about an axis extending along one edge of the product, such as a calendar, a set of maps, an exercise pad, a book, a brochure, a pamphlet or the like. More particularly, the invention relates to improvements in a method of and in an apparatus for turning one outermost sheet of each of a series of successive stacks of sheets, which are held together by a binder for pivotal movement about a predetermined axis, so that the one outermost sheet is moved away from the adjacent (neighboring) sheet and into contact with the outer side of the other outermost sheet of the respective stack.
Turning of sheets in the just outlined manner is desirable and advantageous in connection with the making of stationery and like products of the type wherein the stack contains two cover sheets and the cover sheets are adjacent each other in the course of the binding operation, e.g., during insertion of a spiral binder or a so-called wire-O (trademark) binder into a row of perforations along one edge of the stack of overlapping sheets. The rear cover sheet overlies the front cover sheet in the course of the binding operation and is thereupon pivoted about the axis of the freshly inserted binder so as to overlie the rearmost sheet of the stack of sheets between the two cover sheets. Such mode of making and processing stationery products which have front and rear cover sheets is desirable and advantageous because the seam which develops at the locus of closing a C-shaped binder in order to convert its prongs into rings can be concealed between the rear cover sheet and the adjacent sheet so that it cannot detract from the appearance of the finished product.
One presently preferred mode of assembling stacked paper sheets with or without cover sheets with binders, particularly wire-O (trademark) binders, is disclosed in commonly owned U.S. Pat. No. 4,558,981 granted Dec. 17, 1985 to Fabrig. The disclosure of this patent is incorporated herein by reference.
The cover sheets of an exercise pad, a brochure, a book or another stationery or like product can be made of a material which is different (in texture, color, thickness, stiffness and/or other characteristics) from the sheets of the stack between the two cover sheets. Many machines for assembling stacked sheets with binders are designed in such a way that two identical or different cover sheets are placed on top of the stack of regular or inner sheets prior to the making of perforations along one edge of the stack but not later than immediately prior to insertion of the binder.
German Auslegeschrift No. 26 20 688 discloses an apparatus which is designed to turn the rear cover sheet of a freshly formed stationery product (e.g., an exercise pad with a stack of paper sheets and two cover sheets which may but need not be made of paper) so that the rear cover sheet is moved from the outer side of the front cover sheet to the outer side of the rearmost paper sheet. The pad which is provided with a freshly inserted binder rests on an inclined plate and is transported from the plate to a turning apparatus including a turning device, an intermediate conveyor and a removing conveyor operating at right angles to the intermediate conveyor. The turning device turns the entire pad from a non-horizontal position which is determined by the aforementioned plate to a horizontal position in which the turned pad comes to rest on the intermediate conveyor. When the turning device completes the turning of the entire pad and is moved back to its starting position, it entrains the rear cover sheet and releases it in a position such that the entrained rear cover sheet is spaced apart from the front cover sheet and hangs by gravity outside of the range of the turning device as soon as it begins to advance with the intermediate conveyor. The pad is thereupon pushed off the intermediate conveyor and onto the removing conveyor in a direction at right angles to the direction of transport of pads on the intermediate conveyor; at such time, the partially turned rear cover sheet is turned again to abut the outer side of the rearmost sheet of the stack of sheets between the two cover sheets.
A drawback of the apparatus which is disclosed in the Auslegeschrift is that turning of the rear cover away from the front cover and against the outer side of the rearmost sheet of the stack in the respective pad necessitates a substantial change of orientation of the entire product (such as a pad), i.e., of a relatively large mass with attendant problems regarding accurate guidance, energy requirements, controlling the inertia of the product and others.